(1) WHAT DID THEY SEE INSIDE ATOM?
If we forget the man made “alloys” which are mixtures of metals, we can see that every pure metal is an “element “i.e. one among the 92 building bricks of the physical world. But the arrangement of “internal parts” atoms in a piece of metallic element is somewhat different from the way we find in nonmetals. The arrangement of atoms even in a tiny metal block is like a very very tough three dimensional structure having billions upon billions of positively charged nuclei fixed immovably along x , y and z axes in a jelly of negative particles(electrons). .But before we go further to learn about these arrangements of atoms in a block of a metallic element, we should understand a surprising new fact. It is really one of the greatest secrets of nature learnt by scientists after ingenious experiments.
We know that all matter of the physical world is made of 92 types of atoms which correspond to the 92 elements. Scientists wanted to study the interior of the atom and in their imaginations reduced themselves to the size of atoms themselves! Scientists can construct mathematical models in their brains when suitable laboratory equipment is not still available. In fact most of the theories in modern atomic physics and chemistry can be traced to this type of mathematical modeling by expert scientist- mathematicians in their brain chambers.
The scientists used very high voltage electricity (of the range of twenty thousand volts) to attack the unbelievably minute atoms to study how they behave under such force. originally they wanted to know if current can jump across a gap in electric circuitpassing through a sealed evacuated glass tube. They kept the gas/air at extremely low pressure in a sealed glass tube and sent powerful electric discharges through it. They succeeded finally in breaking the atom. They were sure that some invisible rays emanated from the metal block working as negative electrode. They became sure about existence of an “invisible” radiation” because as soon as the apparatus was switched on, glass sheets coated with zinc sulfide lighted up,magnetic and electric fields arranged around the radiation bent its path. Not only this , they learnt that it was a stream of minute negative particles which could turn tiny paper wheels arranged inside the apparatus just as particles i.e molecules in air can turn fans.. The invisible rays therefore should only be a stream of negative particles..
Wonder of wonders! When heavy positive particles (the streams of alpha particles coming out of radioactive substances) were aimed at the atoms of heavy metals (contained in extremely thin wafers of metal foil kept in evacuated sealed glass tubes) not a few of these alpha particles were repelled with great force and some were even pushed back in the direction from which they came. The inescapable conclusion, after several very complicated mathematical calculations, was that the atom should have a very heavy positively charged centre. That center of atom was like an impenetrable fort. Imagine a fort with three meter thick stone walls rising to a height of thirty meters. The atom’s center was like that, so impenetrable! The entire central fort was positively charged because it is filled with very heavy positive particles. Each positive particle was………
Dr. Rutherford could easily imagine (as he entered inside atom in his feats of imagination) that there should be negative particles with a total negative charge equaling thetotal positive charge of the heavy central “positive fort” and that they have to circle at unimaginably gigantic speeds so that they do not get dragged into the nucleus and cause destruction of universe. These electrons are the real source of the entire world’s electricity which runs our machines, fans, computers, TVs etc. Another surprising thing is that if we compare the positive center of atom to an impenetrable rock fort, the electrons can be likened to light ping pong balls! 99.9% of total weight of atom is concentrated in the central fort! The almost weightless electrons fly at terrific speed making millions of billions of rounds each second around the central positive fort (called by scientists as “nucleus”).
The most important thing is this. Each of the electrons circling outside the “positive fort” though very light have negative electric charge exactly equal to that of each positive particles(protons) inside the central fort.It is surprising how the electrons manage to have so much power and energy! We can say that the electrons are truly crystallized energy.
(2) METALS ARE SO DIFFERENT
We know that atoms are only of 92 types. We also know that when an atom is broken (by using 20,000 volt electric current in a specially controlled way) the results led to an inescapable conclusion that inside every atom there is a heavy positive nucleus where all positive charge should be concentrated. Scientists felt that there may be positive particles inside nucleus. All the positive particles must be bound permanently inside the nucleus. Later while studying the streams of particles coming from positive electrode and going towards negative electrode in the discharge tube containing hydrogen gas at very low pressure scientists could confirm that those rays were rays of positive particles. But the positive particles coming out of positive electrode are really groups of positive and neutral particles bound tightly together. They are actually atomic nuclei of the gas used in the discharge tube from which most of the circling electrons are wrenched away. Only when we use hydrogen gas inside the discharge tube we can get single positive particles i.e single particles with the unit positive charge called protons. Even here to some protons one or two neutral particles may be attached. Scientists found that the neutral particles are also necessary to keep the positive fort intact and everlasting. Some small particles are exchanged billions of times per second between protons and neutrons to keep the nucleus strong and everlasting like a rock fort!
The atom is mostly empty. Far away from central positive nucleus the electrons carryingthe total negative chargerotate around the nucleus at terrific speed thousands of billions of times per second. As a result, though every object (both animate and inanimate) is made of billions upon billions of atoms and in spite of the fact that every atom has electrically charged particles inside, still every atom in every object remains perfectly neutral. The world has not exploded in the thousands of billions of years due to electrical accidents from clash of positive and negative charges inside every atom in the universe!
In side every atom the electrons do not go round the nucleus in haphazard groups in haphazard paths. The electrons are arranged “as per strict mathematical formulas” in a number of concentric shells around the nucleus! The electrons rotate at such terrific speed that they appear every where at same time. So the electrons do not appear as particles but form hollow solid shells!
Every atom in universe thus is full of electric power .We should very clearly note at this stage that there are no “positively charged particles” in the electric current which we use in our homes. What we call”electricity” is the electricity coming from the negative electrons. Electricity is nothing but an endless stream of billions upon billions of electrons. It is veritable “Niagara falls” of negative particles. Like a mighty hill stream flowing down from higher level to lower level, the current of negative electrons too travels from “higher electric potential” to “lower electric potential” and on the way turns all our electric machines.
It should be clearly noted that the positive particles are permanently bound inside nucleus and can never move outside and can never be seen out side except in special experiments. What we call “positive terminal” in our electric apparatus like bulbs, switches, motors, electric cells etc does not contain real positive particles but it is only a place with “deficiency in electrons “. It is a place in electric circuit less negative than any other place in the circuit.For example let there be three electrically charged plates A, B &C. Let plate A have five billion electrons, plate B three billion electrons and plate C just one billion electrons. If we compare B and C, we say that B is negative and C is positive. But when we compare B and A we have to say that B is positive and A is negative! Positive simply means fewer electrons. Negative means more electrons.
We know that in any atom the electrons rotate around the positive nucleus thousands of billions of times per second and that the speed is so great that the electrons construct layers of concentric impenetrable shells around the nucleus. In case of metal atoms they too have central” positive forts” and negative electrons circling outside in many concentric shells. In every atom the total negative charge should equal the total positive charge .The metal atoms too must follow this universal law. But the metal atoms follow it in a slightly different way!
Take a small metal object like a spoon or a new nail. We imagine them to be containing billions upon billions upon billions of unmoving stationary metal atoms. In metals there would be a vast endless lake of billions upon billions upon billions of electrons in which positive nuclei are embedded like immovable positive forts. We should also clearly note that the number of positive particles in “positive forts” and the number of electrons circling outside is kept perfectly equal even in the metals just as in nonmetals. All the metal atoms in metal objects (like the spoon and nail) are perfectly neutral . But something is different with metal atoms. Let us become as small as atoms to see what is happening there.(metals freely conduct electricity while nonmetals do not conduct)
A few electrons of the outermost shell do not stick to the atom. They consider themselves free and start wandering between the billions upon billions positive fortsin the sea of electronsin the metal object. The so called negative sea is made only of these loose electrons of outermost shells. However though the electrons of the outermost shells do not stick to any particular atom, they “ know” that their first duty is to keep every atom among the billions upon billions atoms perfectly neutral. So if two electrons left the outermost shell of a particular atom two other electrons from the sea of electrons jump on to the deficient outermost shell of that atom! Such “jumping out” and “jumping in” from/to the electron shells occurs billions upon billons of times each second in every metal object. Such activity exists every moment in the metal spoon, iron nail, gold ring and wire coil which is not connected in any electric circuit.
In a coil of metal wire “not connected to any electric power source” the billions of electrons move at random in all directions like the thousands of people moving in all directions on a very busy city street in evening times. But if the two ends of the wire coil are connected to the positive and negative terminals of an electric cell the situation changes instantly! The billions upon billions upon billions of electrons moving carelessly in all directions come to “attention” immediately, fall in line like disciplined soldiers and start marching from negative pole to positive pole at terrific speed of more than 200,000 kilometers per second! The wire is now live with a terrific current of electrons as powerful as a waterfall.
The electric cell and dynamo are like powerful pumps of electrons. They ensure a nonstop circular flow of electrons in the electric wire. It is just like pumping of water by a motor pump from ground floor to the top floors . An electric cell or dynamo has positive and negative terminals. When one end of a wire coil is connected to the positive and the other end to the negative terminal, a most terrific stream of electrons start to flow round and round in the wire coil just as water current flows in the garden pipe. Thus the electric cell and dynamo acts exactly like a pump.
The big thermal power station from which we get electric current for our homes has huge dynamos. But the speed of flow of electrons (called technically as “current”) and also the “level difference” they produce in the electron current(called technically as “voltage”) are so terrific that a 220 volt current can kill people if live wires are touched carelessly. If we connect electric appliances like TV,radio,computer,fan,electric bulb etc(called technically as “resistances”) on the circuit they all get the required energy and start working.
(3) WHAT IS ELECTRIC CURRENT?
We saw that the electric current is like water flowing through long rubber pipes used in garden. The most important thing is that electric current should circulate in full circles all through the connecting metal wires billions of times per second. Only if the current of electrons “actually passes” through our home- equipment or factory-machinery then only they work.
We have to use the current of required “voltage” to make different equipment work. Voltage is like level of a “waterfall” which we see in the hills. If the waterfall is only two feet high we can walk across it . But if the waterfall is two hundred feet high we can not stop below the huge masses of tumbling water. The electric power passing through the high transmission towers is like such a big waterfall.
If we connect a small torch light bulb to a singe electric cell through two wire paths( “in” route and “out” route) there also appears a powerful current of billions of electrons. But it is like a shallow stream just a few inches deep. The voltage (level difference) is only 1.5 volts. It is utterly powerless. In computer some parts require two different fixed voltages like 10 volts and 5 volts which are also low. Most electronic equipment and telephones also use only such low voltage. High voltage current kills a person .The salty liquids in living bodies fully conduct electric current and electrolysis– a kind of electrical surgery of body parts by electricity — takes place and the muscles all over the body including those near the vital parts like heart and lung contract uncontrollably resulting in instant death.
From practical point of view we can treat the “plug point” in our house (and not the dynamo in power station) as the source of electric power. Here electrons flow (a)from one plug pin to one terminal of our table fan in one wire path and (b)from the other terminal of the table fan to the second plug pin in the other wire path. We can just forget the power plant (but not the power company which sends the monthly power consumption bills!)
We use a switch like a gate which we can close to stop the flow of billions of electrons whenever we want. The switch has two positions. When the switch is”on” the electron flow is permitted. When it in “off” position a gap is created in path of electrons. They can not jump over this gap and the current is stopped and all the electric and electronic equipment become dead. In “switch on” position a metal strip creates path across the gap. In “switch off” position the metal strip is removed.
When we talk of a”positive terminal” it is only to indicate a connecting screw ( in the electric cell or other electric equipment) where billions of electrons are “flowing out” and creating a great deficiency of electrons at that point. We use the word “negative terminal ” to indicate the end to which billions upon billions of electrons are flowing in and accumulating. We should remember that we can not at all see the “real positive particles ” that exist in atoms. They are sealed and jailed and bound for ever in the “central fort” of atom.
Before Faraday invented the theory about dynamo and motor all electric machines were tiny toys in laboratories. Only after his invention engineers improved it and constructed giant size dynamos and electric motors and started the age of electricity.